Aromatic polycarbonates form a class of thermoplastic polymers that offer some excellent engineering properties such as high stiffness, good melt processability, good elongation properties and high impact resistance. On the other hand, they have some limitations in strength and environmental stress cracking resistance, and, to a lesser extent, in fire resistance (as typically quantified by the burn time). In certain demanding industries, the level of properties achieved by aromatic polycarbonates in terms of strength and environmental stress cracking resistance is insufficient. In certain still more demanding applications which may be found in industries like commercial aviation and other civil transport, an increased fire resistance is needed, as well as a still higher strength.
Polyarylenes, especially polyphenylenes, exhibit an exceptionally high strength; they exhibit also an exceptionally high hardness, scratch resistance and dimensional stability. As concerns these properties, the level of properties achieved by neat polyarylenes usually exceeds by far that required by the most severe end uses. Unfortunately, polyarylenes have serious limitations in toughness-related properties, in particular in terms of impact resistance and elongation properties.
To meet the primary need for increased strength and environmental stress cracking resistance, it has already been tried to blend aromatic polycarbonates with certain classes of polyarylenes, in particular with Parmax® 1000 and Parmax® 1200 polyphenylenes (Parmax® 1200 is now commercialized by SOLVAY ADVANCED POLYMERS under the trade name PRIMOSPIRE™ PR-120). While, in these aromatic polycarbonate-polyarylene blends of the prior art, the polyarylene provides indeed a higher level of strength (which meets sometimes the requirements set by the application), these blends have still essentially the same limitations in terms of environmental cracking resistance. Besides, as the skilled in the art may have have dreaded in the light of the properties of neat polyarylenes, the prior art aromatic polycarbonate-polyarylene blends suffer from some limitations in terms of elongation properties and impact resistance; also, they have rather poor, or even poor, melt compatibility and processability, which probably explains why the skilled person generally prepared them by solution blending. Finally, no fire resistance increase is obtained; to the contrary, the blends polycarbonate-Parmax® 1200 blends exhibit even a somewhat lower fire resistance.
Polymer blends have been widely taught and employed in the art. As broad as this statement may be, the blending of polymers remains an empirical art and the selection of polymers for a blend giving special properties is, in the main, an Edisonian-like choice. Certain attributes of polymer blends are more unique than others. The more unique attributes when found in a blend tend to be unanticipated properties. According to Zoller and Hoehn, Journal of Polymer Science, Polymer Physics Edition, vol. 20, pp. 1385-1397 (1982): “Blending of polymers is a useful technique to obtain properties in thermoplastic materials not readily achieved in a single polymer. Virtually all technologically important properties can be improved in this way, some of the more important ones being flow properties, mechanical properties (especially impact strength), thermal stability, and price. ( . . . ) Ultimately, the goal of such modeling and correlation studies should be the prediction of blend properties from the properties of the pure components alone. We are certainly very far from achieving this goal.”
There remains a strong need for a polymer material offering a superior balance of properties, including at least part of, and preferably all, the following ones:                high strength, higher than that of prior art neat aromatic polycarbonates;        high stiffness, as high as that of prior art neat aromatic polycarbonates;        high environmental stress cracking resistance, higher than that of prior art neat aromatic polycarbonates and that of prior art aromatic polycarbonate-polyarylene blends;        fire resistance properties in progress with regard to those of the prior art aromatic polycarbonate-polyarylene blends;        impact resistance properties in progress with regard to those of the prior art aromatic polycarbonate-polyarylene blends, ideally approaching by certain aspects that of the neat aromatic polycarbonates;        elongation properties in progress with regard to those of the prior art aromatic polycarbonate-polyarylene blends;        good melt processability, in substantial progress when compared to that of the prior art aromatic polycarbonate-polyarylene blends.        
Further, to be suitable for use in certain applications of the most demanding industries, such as commercial aviation and other civil transports, the polymer material should further offer:                very high strength, higher than that of prior art neat aromatic polycarbonates and that of the prior art aromatic polycarbonate-polyarylene blends;        very high fire resistance properties, higher than that of prior art neat aromatic polycarbonates and that of the prior art aromatic polycarbonate-polyarylene blends.        